1. Field of the Invention
This invention concerns cut-off machine for mills which produce continuously emanating elongated workpieces of constant cross-section, such as welded tubing, and more particularly concerns cut-off machines of the type in which a cut-off die set is caused to be operated during traversing movement with the workpiece as it emanates from the tubing mill.
2. Description of the Prior Art
The so called ram type flying cut-off machines have enjoyed considerable success, since the precision ways and other complicated costly structure required in alternate approaches to this problem are greatly simplified or eliminated while reliability is improved an maintenance requirements reduced.
Similarly the associated controls are considerably reduced in complexity since a common drive comprising a rotary crank produces both the clamping chuck and cut-off blade stroking movement.
One example of one of these machines is described in detail in U.S. Pat. No. 3,288,011 and includes a ram which is supported on a machine frame by means of a plurality of links pivotally connected to the machine frame at their upper ends and pivotally connected to the ram at their lower ends which links thereby provide for to and fro reciprocation or "swinging" movement of the ram back and forth through an arcuate path in a plane parallel with respect to the longitudinal axis of the machine. The ram carries upper rails retaining an upper carriage for mounting of the cut-off die set while lower pairs of rails are disposed beneath the ram affixed to the machine frame slidably carrying the lower carriage support for mounting of the cut-off die set. The ram is caused to swing on the links by an actuating mechanism including a rotary crank drivingly connected to the ram by means of a connecting rod so that rotation of the crank arm produces "swinging" movement of the ram. Upon downward movement of the ram moving in its arcuate path a distance sufficient to actuate a cam means which operates the chuck jaws to engage the workpiece, the die set is clamped to the moving workpiece and thereby traversed along the rails therewith. The swinging movement of the ram also produces reciprocation of the cut-off blade after the chuck jaws have engaged the workpiece to sever the particular length of the workpiece. Continued rotation of the crank produces a return swinging movement of the ram, causing a withdrawal of the cut-off blade and unchucking of the workpiece, releasing the die set from the workpiece, after which the die set is returned to the start position by a carriage return mechanism.
The great advantage of this approach notwithstanding, a drawback was nevertheless entailed in the adoption of these designs in that the variability of the shut height, i.e., the position of the ram with respect to the lower support rails at the lowest position of the ram, was not adjustable as it was in some alternative approaches. This lack of adjustability limited the use of die sets requiring different strokes or shut heights in such machines, since some variation in the design of die sets exists. These variations result from the fact that die set designs typically originate from various sources, i.e. various machine manufacturers, tubing mill operators, etc. Also, die set designers sometimes assume some adjustability of the cut-off machine stroke and shut height can be made. The significance of the shut height of the ram is in its relationship to the blade position at its downwardmost position. In some cases the lack of adjustability would produce a blade position extending beyond the cut-off point, which reduces blade life and increases power requirements due to the unnecessary engagement of the blade with the stock. In other cases, particularly for workpiece cross-sections other than tubular, the correct blade position is essential to proper operation of the die set, necessitating shimming or some other modification of the die set in order to render it usable in this type of machine.
The use of adjustability features in the die set itself have in the past been provided, and can correct for some differences in shut height, but the difference in stroke would remain uncorrected.
In other ram support configurations in which the ram is orbited entirely about the link supports stroke increases and decreases would produce inverse decreases and increases in shut heights, which relationship is converse to the adjustments which would be desired, i.e., greater strokes would normally require greater shut heights.
Accordingly, it is an object of the present invention to provide a swinging ram cut-off machine in which adjustability of both the ram stroke and shut height is provided in which both the stroke and shut height may be adjusted so as to vary concurrently, i.e. an increase in strokes will be produced simultaneously with an increase in shut heights, so that a machine may be simply and quickly adapted to die sets which operate with a range of strokes and shut heights.